1. Field of the Invention
The present invention relates to a technique of correcting image blurring of a captured image arising from a shake of an image capturing apparatus by using a method of deforming an image in the image capturing apparatus.
2. Description of the Related Art
In recent years, an image stabilization function has become popular along with the development of a technique of correcting a shake acting on an image capturing apparatus. The image stabilization function corrects not only image blurring of a captured image caused by a camera shake when a user is in a still state, but also image blurring of a captured image generated in shooting while the user is walking. When the user shoots an image while walking, the following image blurring is generated in the captured image, in addition to image blurring of the captured image in the horizontal and vertical directions. Examples are image blurring in which a captured image rotates owing to rotation of the image capturing apparatus about the optical axis, and image blurring in which a captured image is distorted into a trapezoidal shape owing to a tilt of the image capturing apparatus with respect to an object.
As a method of correcting various kinds of image blurring generated in a captured image in shooting while walking, there is known a method of calculating the image deformation amount of a captured image and deforming the image to cancel the image deformation amount (see Japanese Patent Laid-Open No. 2011-146260). Also, as a method of calculating various image deformation amounts of a captured image, there is known a method of calculating an image deformation amount by using a motion vector obtained from a captured image, in addition to a sensor such as an angular velocity sensor (see Japanese Patent Laid-Open No. 2009-124597).
In the technique disclosed in Japanese Patent Laid-Open No. 2011-146260, the amount of deformation generated in a captured image owing to a shake acting on the image capturing apparatus is decomposed into deformation components of translation (horizontal/vertical), perspective (horizontal/vertical), enlargement/reduction, rotation, and shear. Filtering processing and the like are then performed for the respective deformation components, and a projective transformation matrix (homography matrix) is calculated. However, since filtering processing and the like are performed for each deformation component acting on the image capturing apparatus, the calculation amount becomes very large and processing becomes complicated.
In the technique disclosed in Japanese Patent Laid-Open No. 2009-124597, a correction amount for rotation is calculated using a sensor such as an angular velocity sensor, and a correction amount for translation is calculated using a motion vector. However, in a shooting situation in which no motion vector can be detected accurately, the detection accuracy of image blurring caused by translational motion drops, resulting in poor video quality. For example, the contrast of a captured image may become extremely low depending on an object. At this time, the detection accuracy of the motion vector may decrease.